Assembling carbs

I'm aware, and was the "other poster" who made the smoothness comment (and also corrected my brainfart).
No need to send me pics. We have plenty that show what the insides are like,
Inside your Carbs

 

Ok. Well I actually got nervous when i saw the tip poke thru the carb, I was like," oh crap", I went beyond soft seating. But after reading I now see that was ok. I have to change the o-rings, the only thing that came out was the mixture screw and spring, so i will dig around for the washerand o-ring, maybe they get stuck in the seat over time.

 

The o-rings do get stuck easily. Take a sewing needle, heat it with a lighter, and bend the tip into a hook. You now have an o-ring retrieval tool.
Chacal has the correct o-rings in stock, and at a pretty good price if you can't find correct new ones locally.

 

What's the consensus for backing out mixture screws on stock XJ750 Seca... 2.5, 2.75 or 3 turns

 

2.75 is likely a better choice on any of the XJs but the standard is 2.5.

 

Guys, I put the carbs back on after the bench sync, (paperclip method( kudos to author)), and got the butterflies to "half" cover the front hole. I still cannot get over the nearly impossible task of re-installing the carbs. On my XJ750, it took me over an hour. First I confirm the air side boots are pulled out and sit in their boot groove, slide the carb in, so it's lined up(2 minutes), then the fun begins. I tilt the carbs downward, so upper lip of carb can catch inside upper lip of air boot (the boots get hung up on all 3 carb air intakes( r,l top). You need a non-sharp tool that has a 90 deg turn and long enough to release the boot edges from where they hang up(marv mystry on all boot mouths and carb lips(exh,int).
Lots of pulling and pushing,wiggling to finally get carb into air boot, then unhook edge of carb rack which hangs up on the engine side boots, push down and 'back', line up, then shove forward into engine side boots. Screw the braces down.

I tried the first time, pushing the air boots into airbox, slid carbs in and the carbs went onto the engine side much easier....but it was impossible to "pull" the air boots back out and into their boot groove. I wanted to avoid damaging these boots with prying tools, saw my folly and removed the carbs.

 

install carbs to motor first.
you can loosen the bolts on air box to get some play
then start with #3 airbox boot heat it in very hot water this will soften it enough to install in box and on carbs. next boot#2.

 

make one out of 1/8 music wire
grind a cheapo philips screwdriver so the end is round, push the air boots around with it
i push the boots into the airbox

 

I just use my fingers, but then my airbox boots are pretty soft still.

 

Yep, I did this to remove the carbs. But reversing the process doesn't work.

 

It works for me, and a lot of others. You just need practice.
I've gotten to where I can pull the airbox boots back out and into place with just my fingers.

 

It might also be an issue that my airbox boots are 30+ yrs old. If I bought new ones, the rubber shouls be more flexible no? Do you add any lubricant to boots?

 

Mine are the same age as yours. I don't lubriate the airbox boots. I just get them warm (unless it's summer).
New ones will be more flexible, for a while.

 

Roger that.
On other note, I bought the sync tool, will pull the two bolts and clean chamber with wire brush n Hoppes. I was reading if engine gets too hot, the o-rings can melt and the tool can get stuck in the chamber. Doesnt the sync have to be done with a warmed up engine though, with rpms at around 2500?

 

Helpful tip. Don't use the YICS blocking tool. Its not needed in order to get a good running synch.

 

Well let me say this I did buy a yics tool but mine is the rod with the O-rings and you attach a long screw to it to slide it in and there's probably a half inch of play once she said it in there and then supposedly you put the second nut on close it up and then run around forever with this yics tool just in there and you never take it out and in the event that you ever do you know you change the the O-rings then of course there's a tool that shows on the xjbikes website which has that rubber stopper looks like a cork and stops it is specific position is the other guy right in saying you can put the yics tool in or should I just clean the port out like I did already and close it back up

 

So you are saying don't bother with this $28 tool that I bought and just clean the port out put the nuts back on and go ahead with the sync.
I'm sure this is going to beg the question as to why we need to have a sink tool or why Yamaha Engineers think we need to have a sink tool to properly do a vacuum sink is that so should we all be agreeing in this format that's BS

 

The one reason I could see needing a sync tool would be in the event that you were only syncing carbs in pairs and wanted to isolate the other pair

 

it is the risk vs reward issue. we have had a few members break the port when removing bolts that have not been of the bike for decades.
tuning with the sync tool is not going to give you much in the way of performance. syncing with out the tool is syncing how your bike runs real world.

 

It's also a matter of perfection vs. good enough that you can't tell the difference.
Unlike Yamaha, we don't have to make sure the bike passes emissions testing (even Ye-Olde Corner Motorcycle Shop has to adhere to federal regulations regarding emissions, though that isn't enforced). Carb synchronization has the potential to cause a machine to fail even the loose emissions standards of the 80's.

The synch to get from using the tool is (to me) indistinguishable from the synch you get without it. Though there is a strong case for the potential need to use the tool on an engine that is experiencing a realtively broad difference in wear across any two cylinders.

I would not reccomend the blanking tool, since that is meant to permanantly disable the YICS system. The result being a tradeoff: slightly less effort when setting the carbs up, but a loss in fuel economy. It can be used to synch with, but is less handy for that purpose.

If you wih to synch with either tool you can, but the extra time and effort is not worthwhile IMO (several of us here share that opinion, but the collective has no definitive position and there are dozens of conversations about that dating to the start of the forum).

As a side-note: When I tore my engine down to swap cases I found that the YICS ports were very lightly covered in carbon, with no restrictions (it looked like what you'd see after putting smoke on a bullet mould to keep the sides from sticking). The engine had around 20,000 miles on it at the time. I did clean the ports since the head was off, and everything easily accessible, but I'd wager that cleaning would not be warranted that soon (or even regularly) unless the engine was burning oil (blowby getting from the breather into the airbox, and then getting sucked back into the YICS ports would cause more carbon to be deposited).